The invention relates to methods for welding tubes. The invention further relates to a modular machine for carrying out the invention.
Butt welding of tubes, e.g. by high-frequency welding, is known. DE-C-4432674 indicates a special holding device for the welding of thin-walled tubes that are welded e.g. by laser. There is an increasing demand, especially in the motor vehicle industry, for thin-walled tubes of extremely wide range of sizes which after welding can be shaped into body components by high pressure forming. xe2x80x9cThin-walledxe2x80x9d is generally understood to mean tubes with a diameter to material thickness ratio of over 65. There is a demand for welding machines that are capable of economically welding such tubes in various shapes and sizes, and in quantities ranging from individual experimental models to series production runs.
Hence one fundamental problem of the invention is to provide a method whereby tubes in an extremely wide range of shapes and sizes can be presented for welding without costly retooling of the welding machine.
The present invention in one aspect, involves welding preformed tube-rounds into tubes by acting on the tube round at a plurality of points on its circumference simultaneously with pinching tools. The pinching tools are susceptible to individual power assisted adjustment toward and away from the longitudinal axis of the tube round.
By effecting the initial positioning of the tube-round by means of tools with power-driven adjustment, a multitude of tube shapes and sizes can be welded, with each new adaptation involving only a resetting, not a replacement, of the tools.
Another fundamental problem of the invention is, in respect of the welding tool itself, to achieve an optimal welding position for the welding edges of the tube-rounds positioned and/or centered in it, without lengthy setting operations.
To solve this problem, the preformed tube-rounds are welded in a method in which at least one driven adjustable element is used to modify the position of the edges of the tube round to be welded in advance of the welding tool and in response to an edge position detecting device.
The facility for affecting the positioning of the edges by means of elements with powerdriven adjustment allows welding, particularly laser welding, to be carried out is with the edges optimally located in relation to each other. It is also a fundamental problem of the invention to provide a welding facility that combines the greatest possible versatility in terms of tube shapes and sizes and quantities to be welded, with optimal welding results under these changing requirements.
This is accomplished with a machine with aninitial-centring module, and with acentring and welding module
Making the machine of modular construction and arranging the individual modules on a carrier so that they are exchangeable and adjustable with respect to each other mean that optimal adaptation can be made to each to size and shape to be welded. Thus, several lead-in modules and initial-positioning modules can be provided according to the length of the tube and/or such modules can be quickly exchanged for modules adapted to the diameter-range of the tube. Also, by exchanging the centring and welding module, different welding means can easily be used. Preferably, modules are displaceable on the carrier unit so that they can be transferred into an inactive standby position, in which they do not interfere with the working of the active modules and from which they can easily be transferred back into the working position.
With an initial-centring module, it becomes possible to weld tubes of extremely diverse shapes on the same machine.
The centring and welding module provides for adjustment of the position of the edges of the tube-round in the welding zone and hence optimal welding of different tube shapes and sizes.
A further fundamental problem of the invention is to enable particularly thin-walled tubes to be welded. This is accomplished by a centring and welding module.